html,
body {
    margin: 0;
    font-family: "PingFang SC", "Microsoft Yahei", sans-serif;
}

.contain {
    width: 100vw;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: aqua;
}

.login-form {
    width: 240px;
    height: 220px;
    display: flex;
    /* input,button都是行内元素，所以上下排列需要定义沿着上下方向排列*/
    flex-direction: column;
    padding: 40px;
    border: 1px solid #ddd;
    text-align: center;
    /*为后面的定位准备*/
    position: relative;
    z-index: 100;
    background: inherit;
    border-radius: 10px;
    /*超出部分隐藏掉*/
    overflow: hidden;
}

.login-form::before {
    content: '';
    width: calc(100%+20px);
    height: calc(100%+20px);
    position: absolute;
    top: -10px;
    left: -10px;
    overflow: hidden;
    background: inherit;
    box-shadow: inset 0 0 0 200px rgba(255, 255, 255, 0.25);
    filter: blur(5px);
    z-index: -1;
}

.login-form h2 {
    font-size: 18px;
    font-weight: 800;
    color: #3d5245;
}

.login-form input,
.login-form button {
    margin: 6px 0;
    height: 36px;
    border: none;
    background-color: rgba(255, 255, 255, 0.3);
    border-radius: 4px;
    padding: 0 14px;
    color: #3d5245;
}

.login-form input::placeholder {
    color: #3d5245;
}